Atomizer with graduated liquid feed and manufacturing method

ABSTRACT

The atomizer has a conduit for distributing liquid from a single supply inlet to a plurality of feed holes spaced apart from one another. The cross-sectional area of the distribution conduit decreases at increasing distances from the inlet, thus promoting even distribution of liquid among the multiple feed holes at both high and low flow rates. The rate of decrease of cross-sectional area preferably is made inversely proportional to the viscosity of the liquid. In its preferred form, the atomizer utilizes a converging-diverging nozzle with a cavity resonator to generate sonic pressure waves to atomize the liquid. The distribution conduit of decreasing cross-sectional area is formed by using eccentric cylinders, one inside the other, with the cylinders being farthest apart near the liquid inlet, and nearest together 180* from the liquid inlet.

'United States Patent Bell, Jr.

ATOMIZER WITH GRADUATED LIQUID FEED AND MANUFACTURING METHOD Frank S. Bell, Jr., Tuxedo Park, N.Y.

Inventor:

Assignee: Sonic Development Corporation,

Upper Saddle River, NJ.

Filed: Feb. 28, 1974 Appl. No 446,909

References Cited UNITED STATES PATENTS 2/1952 Andermatt 239/430 X 3/1966 Hughes 239/102 X 8/1966 Denis 239/430 7/1972 Schun'g et al 239/102 X FOREIGN PATENTS OR APPLICATIONS 11/1942 Netherlands 239/424.5

Primary ExaniinerM. Henson Wood, Jr. Assistant ExaminerAndres Kashnikow Attorney, Agent, or Firm-Curtis, Morris & Safford [5 7] ABSTRACT The atomizer has a conduit for distributing liquid from a single supply inlet to a plurality of feed holes spaced apart from one another. The cross-sectional area of the distribution conduit decreases at increasing distances from the inlet, thus promoting even distribution of liquid among the multiple feed holes at both high and low flow rates. The rate of decrease of crosssectional area preferably is made inversely proportional to the viscosity of the liquid. In its preferred form, the atomizer utilizes a converging-diverging nozzle with a cavity resonator to generate sonic pressure waves to atomize the liquid. The distribution conduit of decreasing cross-sectional area is formed by using eccentric cylinders, one inside the other, with the cylinders being farthest apart near the liquid inlet, and nearest together 180 from the liquid inlet.

10 Claims, 2 Drawing Figures ATOMIZER WITH GRADUATED LIQUID FEED AND MANUFACTURING METHOD This invention relates to atomizers and mixers for fluent materials, and particularly to liquid feed systems for such devices.

In a preferred embodiment of the invention disclosed herein, the atomizer generates sonic pressure waves by means of a converging-diverging nozzle and a cavity resonator, and uses the pressure waves to atomize a liquid. Liquids are introduced into the high-speed gas stream moving through and issuing from the nozzle, at various positions within or outside of the nozzle. The resonant sonic pressure wave energy atomizes the liquids into minute droplets of a highly uniform size. When used in burners, such atomizers produce flames of excellent quality over a relatively wide range of fuel flow rates. Such atomizers are shown in US. Pat. Nos. 3,240,253 and 3,240,254. The sonic generators used in those atomizers are shown in US. Pat. Nos. 3,230,923 and 3,230,924. Modified atomizers of the same type are shown in US Pat. Nos. 3,667,525, 3,758,033 and 3,774,846. Each of the above-identified patents is assigned to the assignee of this patent application, and its disclosure hereby is incorporated herein by reference.

Although atomizers and burners constructed in accordance with the above-identified patents are superior to other prior devices and are highly satisfactory for most purposes, a problem has been found in the feeding of liquids, especially low-viscosity liquids such as gasoline, etc., into the atomizers. As it will be explained in greater detail below, at relatively high and relatively low flow rates, the feeding of such liquids sometimes has been uneven. Therefore, it is an object of the present invention to improve upon such atomizers, burners, etc., and upon all atomizers in which similar problems exist, by improving the feeding of liquids into the atomizers so as to make the liquid flow more uniform and to make the spray pattern more symmetrical, at both low and high liquid flow rates. It is a further object to provide such improvements relatively simply and at a relatively low cost.

In accordance with the present invention, the foregoing objects are met by the provision of an atomizer liquid feed arrangement in which multiple feed holes are supplied from a single inlet through a conduit whose cross-sectional area decreases with increasing distances from the inlet. This provides even and steady feeding of the liquids at many different flow rates, including both high and low rates. This structure is provided, quite simply, by forming the distribution passageway between two eccentrically aligned cylinders, one within the other. This forms two branch feed paths, each decreasing in cross-sectional area from the inlet. In manufacturing the device, it is preferred that the rate of decrease in crosssectional area be inversely proportional to the viscosity of the. liquid to be atomized by the device.

Further objects, aspects and advantages of the present invention will be set forth in and apparent from the following description and drawings:

In the drawings:

FIG. 1 is a cross-sectional view of the preferred form of a device constructed in accordance with the present invention, the section being taken along line ll of FIG. 2; and

FIG. 2 is a cross-sectional view taken along line 22 of FIG. 1. converging opposite GENERAL DESCRIPTION The atomizer device 10 shown in FIGS. 1 and 2 includes a housing 12 and a nozzle insert 14 force-fitted into the housing 12. As it is shown in FIG. 1, the nozzle insert 14 forms a central gas flow passageway having a converting portion 20, a cylindrical intermediate portion 22 and a diverging outlet portion 24. A resonator member 16 with a resonator cavity 26 is positioned ooposite the exit opening of the nozzle. The resonator 16 is supported by a pair of support legs 18, only one of which appears in FIG. 1, both support legs being secured to the housing 12.

As it is described in greater detail in the abovementioned U.S. patents, a pressurized gas, preferably air, is introduced into the converging section 20 of the nozzle, and the nozzle is believed to accelerate and expand the gas, and to generate pressure waves. The resonator cavity 26 is believed to resonate and amplify the pressure waves, thus producing high-intensity sonic or ultra-sonic pressure waves. A liquid is fed into the gas stream and is atomized by the pressure waves.

Liquid is fed into the gas stream by means of a single fluid inlet hole 28 in the housing 12, together with a liquid distribution conduit 30 and a plurality of feed holes 32 in the diverging section 24 of the nozzle.

In some prior nozzles, the conduit 30 is a groove of uniform depth. Although that construction has proved quite satisfactory in many uses, such as in burning relatively viscous fuels, special problems have been experienced when it is desired to atomize and burn low viscosity fuels such as gasoline. It has been found that at very low flow rates, the liquid tends to fiow into the gas stream in pulses or surges. At high flow rates, the liquid tends to flow unevenly through the various feed holes; specifically, feed holes 32 which are from the inlet 28 conduct more liquid than those near the inlet. Both of these phenomena tend to cause undesirable distortions in the atomization and burning of the fuel.

In accordance with the present invention, the foregoing problems have been solved neatly and simply in the manner best illustrated in FIG. 2 of the drawings. The conduit 30 is formed by an eccentric groove in the nozzle insert 14. This forms two eccentric cylinders 36 and 38, one inside of the other. Cylinder 36 is formed by a cylindrical bore in the housing 12, and forms the outer wall of the conduit 30. The inner wall of the conduit 30 is formed by the exterior of the second cylinder 38, that is, by the bottom of the eccentric groove. The eccentric relationship of the two cylinders gives the conduit 30 a decreasing cross-sectional area at points increasing farther from the inlet 28. The cross-sectional area of the conduit 30 is greatest at the point 40 nearest the inlet 28, and is smallest at the point 34, 180 away from point 40, where a throat is formed. As it is indicated in FIG. 2 by arrows in the conduit 30, the liquid flows in both directions and around the cylinder 38. Thus, the flow path has two branches. It is preferred that the inlet 28 be at the lower-most position of the nozzle when it is in use.

With high liquid flow rates in the prior arrangement in which the two cylinders 36 and 38 were concentric, it is believed that low viscosity fuel such as gasoline would tend to rush past the openings 32 nearest the inlet 28, with the result that relatively little fuel would 3 flow through those holes. However, when the two streams met at the point 34, the liquid stopped. The result was that more fuel would be fed through the holes near point 34 than those near point 40. The result of this was an uneven distribution of the fuel to the gas flowing through the nozzle, and an asymmetrical spray pattern,;with resulting inefficiencies and undesirable burningipatterns.

At low liquid flow rates in the prior concentric cylinder arrangement, since the holes 32 exit into the di verging portion of the nozzle where a negative pressure exists, liquid tended to be drawn through the feed holes 32. The result, it is believed, was that fuel would be drawn out of the inlet opening 28 before it had a chance to accumulate in any great quantity, would be dispersed through the holes 32, and there would be no further fuel feeding for a time until more fuel accumulated. The result of this was a pulsation of the fuel feeding which led to an uneven atomization pattern, uneven burning of the fuel, etc.

It is believed that the eccentric cylinder arrangement shown in FIG. 2 solved these problems in the following way. The volume of liquid in the conduit 30 varies inversely with the distance from the inlet 28. At high flow rates, this tends to reduce the volume of flow through the openings 32 near point 34, while increasing the volume through the holes 32 near the point 40, thus producing a relatively even distribution of fuel among the eight holes 32 and ensuring a uniform symmetrical spray pattern and uniform burning.

At low flow rates, for some reason which is not fully understood at the present time, the pulsations in the liquid feed have been completely or almost completely eliminated. Thus, the spray pattern is steady, even at low flow rates.

DETAILED DESCRIPTION .Still referring to FIG. 2, it is preferred that the feed holes 32 be located symmetrically with respect to one another, with their axes coinciding at the longitudinal axis 42 of the cylindrical bore 36 and the nozzle throat .22. It also is preferred that the holes be spaced symmetrically with respect to the points 40 and 34. Thus, the angle A defining the angular separation of the first hole 32 from the vertical center line of FIG. 2 is 22 /2, and the angle between adjacent holes is 45, when eight holes are used as shown. It is preferred to use as many feed holes 32 as possible so as to promote a more uniform spray pattern. The inlet 28 is aligned with the point 40 which is midway between two adjacent holes so as to ensure symmetrical flow paths along both of the two branches of the conduit 30.

It is preferred that full advantage be taken of the ability of the sonic-actuated atomizer to operate with a high turn down ratio; that is, with a large ratio between the maximum flow rate and minimum flow rate of liquid atomized by the device. In a device which has been built and successfully tested, the tum-down ratio was around 100 to l; a minimum of A gallon per hour to a maximum of 18 gallons per hour. Other typical at points successively further away from the inlet 28 is made to vary inversely with the viscosity of the fluid to be atomized. Apparently, the problems described above are related to the speeds reached or ease of movement by the fluids in the conduit 30. Therefore, less change in volume of the conduit 30 is needed to produce the desired effect when higher viscosity liquids are used.

The principle used in designing the specific arrangement shown in FIG. 2, which is intended for use with gasoline, a low viscosity fuel, was that the volume of fluid immediately outside of the last hole 32 in each of the two flow path branches should be approximately one-fourth of the volume outside the first hole 32 in each of those branches. Thus, the distance F between the point and the inlet 28 is approximately four times the distance'G between the inner cylinder 38 and outer cylinder 36 at point 34. The eccentricity E of cylinder 40 with respect to cylinder 36 is selected so as to produce the desired amount of volume change.

Referring again to FIG. 1, the feed holes 32 are located fairly close to the start of the diverging section where, as it has been noted above, there is a certain amount of suction which helps draw liquids into the gas stream. However, the location of the feed holes in or outside of the nozzle can vary considerably depending upon the particular use to which the atomizer is to be put.

The dimensions of the sonic generator portion of the atomizer are substantially as described in U.S. Pat. No. 3,758,033 in columns 4 through 6 In particular, it is preferred that the half-angle of divergence of the nozzle outlet section24 range from approximately 40 to 25, preferably between 7 and 15.

The diameter D of the resonator cavity 26 preferably is approximately equal to or slightly less than the flow rate ranges and 3 to 250 gallons per hour, and 20 diameter D*, the throat diameter of the nozzle. The depth L of the resonator cavity 26 preferably is equal to either M2 or AM where A is given approximately by the following equation:

A 1.307 D* M l in which M E is the Mach number of the gas flowing at the exit of the diverging section 24 of the nozzle, and D* is the nozzle throat diameter.

The gas can be supplied at a wide range of pressures from values below 1 pound per square inch gauge (p.s.i.g.) to or more p.s.i.g. However, in automotive applications, the air pressure differential through the carburetor venturi seldom is greater than 3 or 4 p.s.i.g., and usually is considerably lower. Therefore, it is anticipated that such low pressures will be the most desirable.

The pressure at which the liquid issupplied to the inlet 28 can vary considerably from negative values to relatively high positive pressures. The suction in the diverging section usually is enough to draw the liquid into the gas stream without pumping. In use in an automotive engine, the fuel can be supplied by an automotive fuel pump through a needle valve close to or within the inlet 28 of the atomizer. The valve controls the liquid flow volume.

For other details of the sonic pressure wave generator and nozzle, reference should be had to the above-.

identified prior patents.

The dimensions of the parts of the device in the drawings are drawn to scale relative to one another and are taken from an atomizer which has been built and successfully tested. Therefore, the relative dimensions of the parts are to be considered as part of the invention disclosure herein.

The above description of the invention is intended to be illustrative and not limiting. Various changes or modifications in the embodiments described may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention.

1 claim:

1. In an atomizer including a nozzle with gas and liquid inlets and a plurality of spaced apart liquid feed passageways for feeding the liquid into the gas, a liquid manifold for distributing liquid from said liquid inlet to said feed passageways, said manifold having a distribution conduit connecting said inlet with said passageways which conduit decreases in cross-sectional area with increasing distance from said liquid inlet.

2. An atomizer as in claim 1 in which said feed passageways are spaced around the perimeter of said nozzle, and said distribution conduit is loop-shaped.

3. An atomizer as in claim 2 in which said loop has two halves, with each half starting at said inlet and decreasing in cross-sectional area at increasing distances from said inlet until a throat is reached.

4. An atomizer as in claim 1 in which the rate of decrease in said cross-sectional area is inversely proportional to the viscosity of the liquid to be supplied to said liquid inlet.

5. A sonic pressure wave-actuated atomizer including a converging-diverging gas nozzle and a cavity resonator opposite the exit of said nozzle, a plurality of feed holes spaced around the perimeter of said nozzle and positioned to deliver a liquid into the gas flowing through the nozzle, liquid inlet conduit means, and

manifold means forming a distribution conduit of generally circular configuration interconnecting said feed holes with said inlet conduit, said distribution conduit having a cross-sectional area which decreases at increasing distances from said inlet conduit.

6. An atomizer as in claim 5 in which said manifold means comprises a first member forming a generally cylindrically-shaped outerwall for said conduit, a second member, of generally cylindrical shape and having a diameter smaller than the first cylinder forming said outer wall, said second member being positioned eccentrically within said first cylinder.

7. An atomizer as in claim 6 in which said second member has a central gas flow passageway through it forming a portion of said nozzle, and said feed holes extend from the outside wall into said gas flow passageway.

8. An atomizer as in claim 5 in which said feed holes exit into the diverging portion of said nozzle.

9. An atomizer as in claim 5 in which said nozzle has a throat of constant diameter, and the diameter of said cavity is approximately the same as the throat diameter.

10. An atomizer as in claim 5 in which the diverging portion of said nozzle has a half-angle of divergence of between 4 and 25, preferably between 7 and 15, said cavity has a depth of approximately M2 or M4, where:

D*, and said feed holes exit into said diverging section. 

1. In an atomizer including a nozzle with gas and liquid inlets and a plurality of spaced apart liquid feed passageways for feeding the liquid into the gas, a liquid manifold for distributing liquid frOm said liquid inlet to said feed passageways, said manifold having a distribution conduit connecting said inlet with said passageways which conduit decreases in cross-sectional area with increasing distance from said liquid inlet.
 2. An atomizer as in claim 1 in which said feed passageways are spaced around the perimeter of said nozzle, and said distribution conduit is loop-shaped.
 3. An atomizer as in claim 2 in which said loop has two halves, with each half starting at said inlet and decreasing in cross-sectional area at increasing distances from said inlet until a throat is reached.
 4. An atomizer as in claim 1 in which the rate of decrease in said cross-sectional area is inversely proportional to the viscosity of the liquid to be supplied to said liquid inlet.
 5. A sonic pressure wave-actuated atomizer including a converging-diverging gas nozzle and a cavity resonator opposite the exit of said nozzle, a plurality of feed holes spaced around the perimeter of said nozzle and positioned to deliver a liquid into the gas flowing through the nozzle, liquid inlet conduit means, and manifold means forming a distribution conduit of generally circular configuration interconnecting said feed holes with said inlet conduit, said distribution conduit having a cross-sectional area which decreases at increasing distances from said inlet conduit.
 6. An atomizer as in claim 5 in which said manifold means comprises a first member forming a generally cylindrically-shaped outer wall for said conduit, a second member, of generally cylindrical shape and having a diameter smaller than the first cylinder forming said outer wall, said second member being positioned eccentrically within said first cylinder.
 7. An atomizer as in claim 6 in which said second member has a central gas flow passageway through it forming a portion of said nozzle, and said feed holes extend from the outside wall into said gas flow passageway.
 8. An atomizer as in claim 5 in which said feed holes exit into the diverging portion of said nozzle.
 9. An atomizer as in claim 5 in which said nozzle has a throat of constant diameter, and the diameter of said cavity is approximately the same as the throat diameter.
 10. An atomizer as in claim 5 in which the diverging portion of said nozzle has a half-angle of divergence of between 4* and 25*, preferably between 7* and 15*, said cavity has a depth of approximately lambda /2 or lambda /4, where: lambda 1.307 D* Square Root ME2 - 1, in which ME is the Mach number of the gas flowing at the exit of the diverging section of the nozzle, with only gas flow through the nozzle, and D* is the nozzle throat diameter, the cavity diameter is approximately equal to D*, and said feed holes exit into said diverging section. 